In recent years, a device configured to assist parking operation has been studied and developed. The device monitors circumference of a vehicle by a camera mounted on the vehicle, detects a position of a parking frame sectioned by white or yellow lines drawn on a road surface from a monitored image, and calculates a relationship between the position of the vehicle and lanes based on the detected position of the parking frame.
In such a system, there is a high possibility that dirt is clung to a lens of the camera because the system is used in a state buffeted by the wind and the rain outdoors. The system is configured to detect the dirt of the lens and notify the detection to a driver, because, if the dirt is clung to the lens, a subject to be photographed cannot be essentially imaged (see, for example, Patent Literature 1).